This invention relates generally to emergency locking safety belt retractors for use in vehicles for storing a safety belt thereon and for allowing unreeling of the safety belt from the retractor so that the safety belt can be placed about the passenger to restrain him in his seat. More particularly, the invention relates to a retractor which allows uncoiling of the safety belt at all times except during a crash or other emergency when the seat belt locks and prevents further protraction of the belt from the retractor. Basically, this invention relates to an inertia sensitive safety retractor which locks the retractor from further protraction of the belt during a change in inertia of the vehicle; for example, during a crash or sudden deceleration. The locking bar is operated by inertia responsive means including an inertia responsive means including an inertia responsive mass. The present invention includes the provision of adding resilient means between the lock bar and the mass for receiving and storing energy imparted thereto by movement of the mass and for thereby urging the lock bar toward locking engagement with the ratchet wheel through a pawl bounce condition.
At least three basic types of emergency locking retractors have been developed heretofore which are being used commercially. The first type employs a locking pawl which is automatically actuated on a slight retraction of the webbing after an initial protraction of the belt from the retractor. The strap acceleration responsive type automatically locks on a protractive movement of the webbing at an acceleration thereof at a rate above a predetermined rate. In the vehicle inertia responsive type of retractor, the locking mechanism operates in response to change in the inertia of the vehicle in which the mechanism is mounted. In these retractors, depending on the position of the locking pawl and the ratchet wheel when the locking pawl moves to its locking position, a pawl bounce condition can occur. The pawl bounce condition is defined as that which occurs when the locking pawl contacts the ratchet in a tip-to-tip engagement. The dynamics which occur during the pawl bounce condition make it possible for the tip of the locking pawl to engage the tip of the tooth of the ratchet wheel in such a manner that the pawl is rebounded or deflected away from the ratchet wheel rather than moving into its locking engagement with the ratchet wheel. Failure of locking pawl to lock immediately with the ratchet wheel may result in undesirable protraction of the safety belt which increases danger to the vehicle occupant during a crash.
It has been realized that the locking pawl means for emergency locking retractors is needed which, even if pawl bounce occurs, locks assuredly during emergency conditions. There have been prior attempts to solve this problem and they have taken numerous paths. For example, in the patent application to Ziv, Ser. No. 459,539, dated Apr. 10, 1974, entitled "Piggyback Dual Lock Bar," a dual locking pawl means is provided such that one pawl or the other will assuredly lock the retractor upon an emergency condition experienced by the vehicle. There have been other numerous attempts to overcome the problems of pawl bounce, but it is believed that none of these prior attempts have included mechanisms having a construction or mode of operation as contemplated for the within invention.